I hope to clarify what is happening when you send the command 'mh' from math lab using ADInstrument Powerlab as a recording mechanism.
have a look at the link http://cedrus.com/support/stimtracke...4_powerlab.htm
It shows you that bit 6-8 is the event marker 0-2 which gives you a value of 1-7(3 bits) trigger to play with. Keep in mind the location of the bit (6-8) which has a byte value of 32 onwards.
Going back to the command 'mh' which is standard on Stim Tracker you can send the command like "mh" + byte value which will correspond to which ever bit is on.
Example: sending the command ('mh',1) will set bit 6 on in the AD instrument giving the value 32 (byte) in the lab chart software.
Example: sending( 'mh',7) will set all the three bits on (6-8) which will give a digital byte value of 224 in the lab chart.
Note: take note that this values are only the bit 6-8 any bit on from 1-5 will affect the digital byte on the Labchart event.
it took us a while to figure out what's happening and just wanted to share out results because I also get some information in lots of forum.

Any question and clarification you can reply or not sure if you can access our email address here.

Cheers
Al